This application is a 371 of PCT/JP99/01565 filed Mar. 26, 1999.
This invention concerns a method of testing hardness of a micro region. More specifically, it relates to a novel method of testing hardness capable of accurately evaluating the hardness of a micro region such as a nanometer region that can not be measured by a test for macro hardness such as Vickers hardness.
Heretofore, in a Vickers hardness test which is typical for the macro hardness test, the hardness has been determined in accordance with a definition of dividing an indenting force with an area of contact. Since there is no substantial size effect in the macro hardness, the indenting force with force employed is usually properly selected.
On the contrary, in the hardness test for a micro region such as a nanometer region, when the hardness is calculated in accordance with the definition based on a measured indenting force and a penetration depth as usual, it results in a problem that an apparent hardness increases since the size effect is not negligible. Then, it is necessary to eliminate the influence of the size effect. In the existent method, a correlation is determined between a hardness determined at a certain penetration depth in accordance with the definition and a macro hardness, or an indentation curve is approximated by a certain function and a correlation between the parameter and the hardness is determined.
However, the existent study for the correlation with the macro hardness is scarcely considered effective. For an arbitrary sample, the hardness of a micro region can not accurately be evaluated at present.
On the other hand, evaluation for the hardness of the micro region has provided an extremely important subject for the research and development of new metal materials and semiconductors.
In view of the above, it is a subject of the invention in the application to overcome the limit of the prior art as described above in indenting an indenter into a sample and evaluating the hardness of a material based on a relation between an indenting force and a penetration depth, and provide a novel method eliminating the influence of the size effect that the apparent hardness increases in the test for the hardness of a micro region with the penetration depth or an indent depth of 1 xcexcm or less, considering the micro hardness in the micro hardness test in the same manner as in the macro hardness in the Vickers hardness test, and capable of effectively utilizing the existent knowledge for the macro hardness and accurately evaluating the hardness of a nanometer region.
The invention of the application, for solving the foregoing subject, provides a testing method for determining the hardness of a micro region, into which an indenter is pushed, from an indentation curve indicating a relation between a penetration depth observed when an indenter in an arbitrary shape is pushed in and an indenting force, characterized by comprising
(1) measuring, in addition to macro hardnesses, relations between penetration depths observed when an indenter in an arbitrary shape is pushed in and indenting forces, for a plurality types of standard samples,
(2) determining a reference function indicating a macro hardness by standardizing a relation between an indenting force and a macro hardness with the same penetration depth used as an index, for indentation curves of a plurality types of standard samples indicating relations between penetration depths and indenting forces,
(3) measuring relations between penetration depths and indenting forces for arbitrary samples, and
(4) determining the hardness of a micro region from the measured values according to the reference function.
Further, according to the invention of this application, a plurality of standard samples having identical mechanical properties in the micrometer region and the nanometer region are used in the method described above.